[Gc] Question about two-level tree

Mike Spivey mike@comlab.ox.ac.uk
Thu, 16 Jan 2003 18:37:29 +0000


I have been studying the data structures used by the GC, and I'm
puzzled about the two-level tree that's used to find the start of an
object given an interior pointer.  Why is it a good idea to describe
large objects by giving a displacement to the beginning of the object,
rather than having all the entries for the object point to a single
block header for the whole object?  It seems to me that the
displacement idea is just a more complicated way of finding the same
header.

-- Mike